Radar Level Gauge Comprising a Safety Device

ABSTRACT

The invention is a radar level gauge comprising a signal generator for generating electromagnetic waves and an antenna for emitting the electromagnetic waves in a container and for receiving electromagnetic waves reflected by the container. The radar level gauge also comprises a safety device for verifying the functional capability or for improving the measuring quality of the radar level gauge, said safety device having a reflector and an adjustment device and/or a reduction device and being suitably designed to adjust the reflector and/or the reduction device at least between a first position and a second position, in which the reflector reflects the electromagnetic waves in a reduced manner. The adjustment device acts on the reflector and/or the reduction device in a contactless manner.

The present invention relates to a radar level gauge comprising a safetydevice according to the preamble of claim 1.

Radar level gauges with such safety devices are known from prior art,for example from U.S. Pat. No. 8,009,085 B2, and show a signal generatorfor generating electromagnetic waves and an antenna for emitting theelectromagnetic waves into a container as well as for receivingreflected electromagnetic waves from the container, with the safetydevice being suitably embodied to check the functionality of the radarlevel gauge. The safety devices shown in prior art comprise for thispurpose a reflector and an adjustment device, which are suitablyembodied to adjust the reflector at least between a first position inwhich it reflects the electromagnetic waves and a second position inwhich it reflects the electromagnetic waves in a reduced fashion.

The radar level gauges known from prior art are generally used incontainers, usually tanks or silos, which are embodied for storingvarious materials. For example food, drinks, drugs, or fuels are storedin such tanks or silos, so that a touchless fill level measurement isrequired. In prior art, for example the above-mentioned radar levelgauge or alternatively ultrasound-based fill level gauges are known astouchless fill level measuring technologies. Based on their highprecision of measurement and their low susceptibility to malfunctionhere radar level gauges are widely used.

The radar level gauges known from prior art are generally fastened via aflange in the upper area of the tank or silo, with an electronic beingarranged outside the housing and an antenna of the radar level gaugebeing arranged inside thereof. The antenna is aligned in a suitablefashion so that electromagnetic waves, i.e. particularly a radar signal,can be sent in the direction towards the filled in material storedinside the container, and that it can receive electromagnetic wavesreflected by said material. Based on a time difference between emittingthe electromagnetic signal and receiving the reflected electromagneticsignal here a fill level inside the container can be determined.

For the functional control of a radar level gauge, particularly to testits functionality in a safety-relevant maximum fill level, a fill levelat which an automatic protection system prevents any further filling inand perhaps at other relevant fill levels, it is necessary to provide asafety device, which allows a statement regarding the functionality atsaid maximum fill level. For this purpose, it is known in prior artduring a safety test to move a reflector manually into the radiationpath of the radar level gauge in order to test here, even in case oflower fill levels of the container, to check the function of the levelgauge at a desired fill level by inserting the reflector at this filllevel into the radiation path of the radar level gauge and this way togenerate a reflection at the desired fill level.

In radar level gauges of prior art it is also considered disadvantageousthat the known arrangements, due to their mechanic design, generallycannot be sealed from the environment or only with great difficulty andtherefore any application for toxic and/or pressurized substances isimpossible or to a very limited extent only.

Therefore the objective of the present invention is to correct thedisadvantages known from prior art and to provide a further developedradar level gauge as well as a safety device for it not showing any ofthese disadvantages.

This objective is attained in a radar level gauge comprising thefeatures of claim 1 as well as a safety device showing the features ofclaim 16.

A radar fill gauge according to the invention with a signal generatorfor generating electromagnetic waves and an antenna for emitting theelectromagnetic waves in a container as well as for receiving reflectedelectromagnetic waves from the container with a safety device fortesting the functionality and/or for improving the quality ofmeasurements of the radar level gauge comprises a safety device with areflector and an adjustment device and/or a reduction device, with thesafety device being suitably embodied to adjust the reflector and/or thereduction device at least between a first position in which thereflector reflects the electromagnetic waves, and a second position inwhich the reflector reflects the electromagnetic waves in a reducedfashion, and is characterized in that the adjustment device operates ina touchless fashion upon the reflector and/or the reduction device.

Due to the fact that the fastening device acts upon the reflector and/orthe reduction device in a touchless fashion it is possible that theadjustment device and the reflector and/or the reduction device can beinserted into the container and operated separated from each other andparticularly in a sealed fashion. By a seal between the adjustmentdevice and the reflector and/or the reduction device it is also possiblethat a mechanical passage, coupling a motion of the adjustment devicefrom outside the tank into the tank and this way acting upon thereflector and/or the reduction device, is avoided such that overall areliable sealing is possible of the container/tank in reference to theenvironment.

A touchless action of the adjustment device upon the reflector and/orthe reduction device can be achieved for example by a magnetic couplingbetween the adjustment device and the reflector and/or the reductiondevice. By such a magnetic coupling a motion of the adjustment devicecan be transferred easily and relatively reliably to the reflectorand/or the reduction unit.

In a first embodiment the adjustment device transfers the rotary motionupon the reflector and/or the reduction device such that particularlythe magnetic coupling forces can be kept low.

In an alternative embodiment the adjustment device transfer a linearmotion upon the reflector and/or the reduction device. By transferring alinear motion, for example a gravity-induced resetting of the safetydevice can be achieved into the second position, in which the safetydevice reduces the emitted electromagnetic waves or abstains fromreflecting them. This way, the functionality of the radar level gauge isalso ensured in case of a malfunction of a safety device.

Ideally, the adjustment device is arranged in a housing, preferablypressure tight and separated from a measuring environment. This housingmay be connected to a fastening flange, for example, with a seal beingprovided between the housing and the flange, for example via a weldingseam or other sealing means.

This way, a pressure-tight and diffusion-tight separation of theadjustment device from the measuring environment is achieved veryreliably, particularly allowing a use in pressurized and/or toxic media.

Preferably the adjustment device is arranged inside the housing and thereflector and/or the reduction device outside thereof. The housing canbe embodied for example as a cylinder closed at the end and projectinginto the container, which is connected to the fastening flange. Such anarrangement can provide simultaneously a defined alignment of the safetydevice towards the antenna of the radar level gauge so that noadditional calibration and alignment is required.

Preferably the reflector is arranged with its end at the housing suchthat a simple interaction between the adjustment device and thereflector and/or the reduction device can be yielded.

The safety device can for example be embodied such that it automaticallytransfers into a second position, without any operative intervention,and thus also in case of a defect, for example of the adjustment device,ensuring the operation of the radar level gauge.

A particularly beneficial magnetic coupling can be achieved when theadjustment device and/or the reflector and/or the reduction device showat least one permanent magnet. By suitably embodied permanent magnets agood magnetic coupling can be yielded, which depending on the alignmentof the poles of the magnet in reference to each other by the attractingand/or repelling effect allows a reliable switching from the firstposition into the second position and vice versa.

The reduction device can be embodied for example as a sheath, mobile inreference to the reflector, which is pulled vertically upwards by theadjustment device, for example, and this way exposes the reflector. Thereflector can for example be arranged perpendicular in reference to aprimary direction of emission of the antenna and in the second positionexceeded by the sheath, preferably in the radial direction. This way thereflector can also be embodied as a stop for the reduction device sothat a particularly simple mechanic arrangement is yielded.

The reduction device can here be embodied for example such that in thesecond position it reflects the electromagnetic waves away from theantenna so that in reference to the first position here a reduction ofthe reflected electromagnetic waves develops.

In a further development of the invention the arrangement may show asensor for monitoring the position of the reflector and/or the reductiondevice and/or the adjustment device such that an electronic monitoringof the position of the reflector and/or the reduction device is possibleas well. This way, in spite of a spatial separation of the adjustmentdevice from the reflector and/or the reduction device, it is madepossible to monitor the actual conditions inside the container such thatinformation is provided as to whether the adjustment device is actingreliably upon the reflector and/or the reduction device.

In addition to a radar level gauge with a safety device, the possibilityfor retrofitting the safety device may be provided as well. Accordingly,the present invention also refers to a safety device for radar levelgauges showing the above-described features.

In the following the present invention is explained in greater detailwith reference to the attached figures.

The figures show:

FIG. 1 a sketch of the principle of a radar level gauge comprising asafety device in the first position, and

FIG. 2 the radar level gauge of FIG. 1 with a safety device in thesecond position.

FIG. 3 shows another exemplary embodiment of a radar level gauge with asafety device showing a rotary reflector in the first position,

FIG. 4 the radar level gauge of FIG. 3 in a second position,

FIG. 5 a radar level gauge with a rotationally embodied reduction devicein the first position, and

FIG. 6 the radar level gauge of FIG. 5 in the second position.

FIG. 1 shows a schematic illustration of a radar level gauge 1 with asafety device 5, with the safety device 5 being shown in a firstposition I, in which a reflector 7 of the safety device 5 showselectromagnetic waves emitted by an antenna 3 of the radar level gauge 1in a reflected fashion. The radar level gauge 1 is designed in thepresent exemplary embodiment with an antenna 3, which in the presentcase is embodied as a horn antenna. However, other forms of antennas arepossible here, too, without leaving the scope of the present invention.

In the present exemplary embodiment the safety device 5 is designed as acylindrically formed housing 10, with at the end near the container ofreflector 7 being arranged in an alignment perpendicular to a primarydirection of emission A of the antenna 3. The housing 10 is arrangedparallel in reference to the radar level gauge 1 in a fastening flange 6and this way already aligned by the factory and matches the fill levelgauge 1. The safety device 5 further comprises a reduction device 15,which is embodied as a sheath displaceable axially at the housing. Atone end of the reduction device 15 near the flange the device comprisestwo permanent magnets 12, which cooperate with two other permanentmagnets 12 arranged at an adjustment device 9 provided in the housing10. In order to yield higher protection from malfunction of thearrangement, here additional magnets may be arranged distributed overthe entire length.

By a magnetic coupling between the permanent magnet 12 at the reductionunit 15 and the adjustment device 9 it is possible to lift the reductiondevice 15, embodied as a sheath, opposite the forces of gravity from thereflector 7, arranged with its end at the housing 10, which reflector inthe present case also serves as a stop, and expose it as shown in FIG. 1for reflecting electromagnetic waves emitted by the antenna 3. Thehousing 10 can in this embodiment be connected circumferentially withthe fastening flange 6, for example welded, so that an arrangementdevelops which is pressure and diffusion tight. This way a radar levelgauge 1 with a safety device 5 shown in FIG. 1 can also be used fortoxic and/or pressurized media.

In order to allow a magnetic coupling through the housing 10 it isnecessary that it is at least sectionally made from a non-magneticmaterial, for example stainless steel.

An activation of the adjustment device 9, not shown in greater detail inthe present case, can occur manually, pneumatically, or electrically. Inparticular a manual and pneumatic operation of the adjustment device 9is preferred because this way a low susceptibility to the adjustmentmalfunctioning can be achieved in a particularly simple fashion.

FIG. 2 shows the radar level gauge 1 of FIG. 1 with the safety device 5in a second position II, in which the reduction device 15 reflects theelectromagnetic waves emitted by the antenna 3 to an area orientedparallel in reference to the primary direction of emission A of theantenna 3 and thus guides them in the direction of the filled in goods.When compared to the first position I shown in FIG. 1, here aconsiderable reduction of the reflection is yielded, causing the safetydevice 5 to be essentially deactivated. In the position shown in FIG. 2it is also clearly discernible that the reflector 7 in the presentembodiment serves as a stop for the reduction device 15.

If in the exemplary embodiment shown in FIGS. 1 and 2 the magneticcoupling between the operating device 9 and the reduction device 15 wasto operate in an unreliable fashion for whatever reason, additionallythe effects of gravity ensure that the reduction device 15 isautomatically switched into the second position II and thus a regularoperation of the radar level gauge 1 is ensured.

FIG. 3 shows an exemplary embodiment of a radar level gauge 1 with asafety device 5, with the safety device 5 being in a first position I.The switch from the first position I to the second position II, shown inFIG. 4, occurs in this exemplary embodiment as well via a magneticcoupling, which is realized by two permanent magnets 12, with in thisexemplary embodiment the reflector 7 being embodied in a rotary fashion.If in the present exemplary embodiment the adjustment device 9 isrotated in its longitudinal axis, via the permanent magnets 12, whichare arranged at one side at the adjustment device 9 and at the otherside at a reflector 7, this rotary motion is transferred to thereflector 7 such that it can be moved out of the first position I intothe second position II. As further discernible from FIGS. 3 and 4 thereflector 7 is arranged in the first position I such that it reflectselectromagnetic radiation emitted by the antenna 3. In the secondposition II the reflector 7 is removed from the radiation path of theantenna 3 such that no reflection occurs. Similar to the exemplaryembodiment shown in FIGS. 1 and 2, it must be emphasized that thehousing 10 is connected to the flange 6 in a pressure and diffusiontight fashion and this way the safety device can be applied in anadvantageous fashion.

FIGS. 5 and 6 show another exemplary embodiment of a radar level gauge 1and in this exemplary embodiment the reduction device 15, as also usedin the first exemplary embodiment of FIGS. 1 and 2, is designedasymmetrically and in a rotary fashion. In the first position shown inFIG. 5 the reduction device 15 is arranged such that a portion of thereflector 7 is exposed and this way a reflection of electromagneticradiation emitted by the antenna 3 can occur. In the second position II,which is shown in FIG. 6, the reduction device 15 is arranged rotated by180° about its longitudinal axis and completely covers by its asymmetricdesign the reflector 7 when seen from the antenna 3 such that anyelectromagnetic radiation emitted by the antenna 3 is further reduced atthe reduction device 15, or as shown in FIG. 6, further reflectedtowards the filled in goods. In any case it is decisive that a signalreturned by the reflector 7 in the direction of the antenna 3 is reducedin reference to the first position 1.

Similar to the previous exemplary embodiment, a coupling between theadjustment device 9 and the safety device 5 occurs, in this case of thereduction device 15, via two permanent magnets 12 arranged at the oneside at the adjustment device 9 and at the other side at the reductiondevice 15. They transfer a rotary motion of the adjustment device 9 tothe reduction device 15.

LIST OF REFERENCE CHARACTERS

-   1 radar level gauge-   3 antenna-   4 container-   5 safety device-   6 fastening flange-   7 reflector-   9 adjustment device-   10 housing-   12 permanent magnets-   15 reduction device/sheath-   A direction of emission-   I first position-   II second position

We claim:
 1. A radar level gauge comprising a signal generator forgenerating electromagnetic waves and an antenna for emitting theelectromagnetic waves as well as receiving reflected electromagneticwaves, comprising a safety device for checking the functionality or forimproving the quality of measurements of the radar level gauge, with thesafety device comprising a reflector and an adjustment device and areduction device and being suitably embodied to adjust the reflector andthe reduction device at least between a first position, in which thereflector reflects the electromagnetic waves, and a second position, inwhich the reflector reflects the electromagnetic waves in a reducedfashion, wherein the adjustment device acts in a touchless fashion uponthe reflector and the reduction device.
 2. The radar level gaugeaccording to claim 1, wherein the adjustment device comprises a magneticcoupling to the reflector and/or the reduction device.
 3. The radarlevel gauge according to claim 1, wherein the adjustment devicerotationally moves the reflector and the reduction device.
 4. The radarlevel gauge according to claim 1, wherein the adjustment device actslinearly upon the reflector and the reduction device.
 5. The radar levelgauge according to claim 1, wherein the adjustment device comprises apermanent magnet.
 6. The radar level gauge according to claim 1, whereinthe adjustment device is arranged in a housing separated from themeasuring environment in a preferably pressure-tight fashion.
 7. Theradar level gauge according to claim 6, wherein the housing is welded toa fastening flange.
 8. The radar level gauge according to claim 6,wherein the adjustment device is arranged inside the housing and thereflector or the reduction unit outside thereof.
 9. The radar levelgauge according to claim 1, wherein the safety arrangement is embodiedsuch that it automatically shifts into the second position without anyoperational intervention.
 10. The radar level gauge according to claim1, wherein the adjustment device, the reflector or the reduction devicecomprise a permanent magnet.
 11. The radar level gauge according toclaim 1, wherein the reduction device is embodied as a sheath that ismobile in reference to the reflector.
 12. The radar level gaugeaccording to claim 11, wherein the sheath of the reflector projectsbeyond the reflector in the second position and in the radial direction.13. The radar level gauge according to claim 12, wherein the reflectoris embodied as a stop for the reduction device.
 14. The radar levelgauge according to claim 13, wherein the reduction device is embodiedsuch that in the second position it reflects the electromagnetic wavesaway from the antenna.
 15. The radar level gauge according to claim 1,wherein the arrangement comprises a sensor for monitoring the positionof the reflector and the reduction device.
 16. The radar level gaugeaccording to claim 1, wherein the adjustment device is drivenautomatically.
 17. The radar level gauge according to claim 1, whereinthe adjustment device is coupled to a field device.
 18. A safety devicefor the radar level gauge of claim 1, comprising a reflector and anadjustment device and a reduction device and being suitably embodied toadjust the reflector and the reduction device at least between a firstposition, in which the reflector reflects the electromagnetic waves, anda second position, in which the reflector reflects the electromagneticwaves in a reduced fashion, wherein the adjustment device acts in atouchless fashion upon the reflector and the reduction device.